1. Field of the Invention
The present invention refers to an apparatus for clamping workpieces which have to be machined by a machine tool, the clamping apparatus comprising a rectangular frame means including two longitudinal frame members and two transverse frame members, and clamping means adapted to fix the workpieces to be machined to the rectangular frame.
Further, the invention refers to a clamping bar adapted to be used in an apparatus for clamping workpieces which have to be machined by a machine tool.
2. Prior Art
If a workpiece is to be machined by means of a machine tool, the workpiece has to be fixed or clamped in a suitable manner to the worktable of the machine tool or within the working area of the machine tool. It is well known in the prior art to provide the worktable of the machine tool with undercut grooves which are adapted to receive displaceable clamping bolts. By means of such clamping bolts and additionally by means of hoop-shaped fasteners a workpiece to be machined can be fixed to the worktable of the machine tool. Such a clamping method is cumbersome and time-consuming and often not suitable for small workpieces.
Furthermore, a clamping apparatus is known which comprises a frame provided with clamping members. Usually, according to a well known embodiment, one side of the frame is in the form of a stationary clamping jaw, and a further, displaceable jaw is provided which is under the influence of one or several clamping screws, spindles or the like. Thus, the workpiece to be clamped can be fixed between the stationary and the displaceable jaw.
A main drawback of such a known clamping apparatus is that only one single or several workpieces having exactly identical size can be clamped. Another drawback is that such a clamping frame comprising a fixed and a displaceable jaw, if it is to be used for the clamping of big workpieces or a plurality of identically sized small workpieces, is either to flexible since it resiliently deforms during clamping of the workpiece and workpieces, respectively, or is extraordinarily bulky and heavy if it is to be designed with the required rigidity.
In many applications, particularly if a workpiece has to be machined by wire erosion, it is of paramount importance that the clamping frame be designed to be open such that the erosion wire can pass through the clamping frame. This request renders it even more difficult to design such a clamping frame such that it posses the required rigidity without being too bulky and heavy.